Copper base alloy



Aug. 6, 1940- J. M. KELLY CPPERl BASE ALLOY Filed March 16, 194Q INVENTOR Patented ug. 6, 1940 PATENT OFFICE COPER BASE ALLOY James M. Kelly, Trafford, Pa., assigner to Westinghouse Electric & Manufacturing Company,

East Pittsburgh, Pa.,

Sylvania Application March 16,

3 Claims.

This invention relates to copper base alloys, and in particular to copper base alloys of the aluminum-bronze type.

Alloys of aluminum and copper are known in 5 the industry and are employed where the characteristics of corrosion resistance are required. The known copper-aluminum alloys are, however, limited to certain applications which do not require high physical strength and hardness.

It is an object of this invention to provide a copper base alloy of the aluminum-bronze type which-will have high physical strength together with corrosion resistant characteristics.

Another object of this invention is to provide a copper f base alloy of the aluminum-bronze alpha type which may be precipitation hardened and cold worked to impart high physical strength thereto.

Other objects of this invention will become apparent from the following description when taken in conjunction with the accompanying drawing, the single i'lgure of which is a graph, the curves of which illustrate the hardness values obtained for representative alloys of this invention.

The alloys of this invention are prepared in accordance with standard melting practice from copper, aluminum and iron. Suicient aluminum is employed to give an aluminum content of from 5% to 7%, while the iron content in the copper base ranges from 1% to 5%. These alloying elements cooperate to give an aluminumbronze alloy of the alpha type which is resistant to oxidation, and which can be heat treated and cold worked to impart a high strength to the alloy.

In order to develop the mechanical strength of the alloy, it is subjected to a precipitation hardening treatment comprising subjecting the alloy to a high temperature below the melting point of the alloy for obtaining 'a high solid solution of the iron in the alloy, quenching the alloy from the high temperature to retain the iron in solid solution, and then reheating or ageing the alloy at a lower or ageing temperature for a period of time suiicient to precipitate the iron from the solid solution state. In practice, heating the alloy at a temperature Ybetween '750 and 1025" C. is found to effect a high solid solution of the iron in copper, while reheating or ageing the alloy at a temperature of between 350 and 650 C. eiec'ts the precipitationy of the iron to impart the desired characteristics t the resulting alloy.

As a specic example of the improved hardness characteristics obtained with the alloy of this invention, reference may be had to the accoma corporation of Penn- 1940, Serial No. 324,434 (o1. 'J5-159) Composition Alloy Nm Pecnt Pei-Aclent Pecnt In the drawing, curves 0, I, 2, 3 and 5 represent the results obtained with the alloys in the order given in the table and containing 0, 1, 2, 3 and 5% of iron, respectively, after they were subjected to a heat treatment consisting of quenching them from a temperature of 950 C. and ageing them at a temperature of 500 C.- for diiferent periods of time. From these curves, it is quite apparent that the iron is quite effective in cooperating with the aluminum in the copper base to give an alloy of improved characteristics. This is quite apparent from a comparison of curves I, 2, 3 and 5, which represent the results obtained with the alloys of this invention, with the results shown by the curve 0, which represents the results obtained with a binary copper-aluminum alloy.

The alloys of this invention have very good thermal endurance characteristics, that is, the characteristic to retain its hardness at elevated temperatures, as is evident from an examination of the curves of the drawing. These copperiron-aluminum alloys have been found to retain their highstrengths even when subjected to temperatures of 850 C. for short periods of time.

With the copper-iron-aluminum alloys of this invention-it is found that high tensile strengths can be obtained in the heat treated state, or wherejit is desired these 'high tensile strengths can be further improved by subjecting the heat treated alloy to, cold work. As illustrative of the high tensile strengths obtained with the alloys of this invention, both in the heat treated cast con- Tensile strength, pounds per square inch Alloy N o.

Treatment Treatment A IB In obtaining the results listed in the foregoing table, each of the alloys was subjected to each of two treatments, Treatment A consisting of quenching the alloy from a temperature of 1000 C. and ageing it for twenty hours at a temperature of 500 C., while Treatment B consists of a similar heat treatment with the addition of supplementary cold workin the amount of a 25% reduction inv area. Thus the alloys of this invention have the advantages of the alpha type binary alloys, in that they are susceptible to precipitation hardening treatment, while at the same time having suiiicient duetllity to permit the cold working of the alloys to further improve the characteristics.

As a further advantage of the alloys of this invention containing from to 7% of aluminum and from 1% to 5% of iron with the balance copper, it is found that they have the desirable characteristic of being resistant to oxidation when subjected to heat at elevated temperatures. As a specific example of the oxidation resistant characteristics of the alloys of this invention, when articles formed from the alloys were placed in a large electric furnace in which there was a free circulation of air and heated at a temperature of 850 C. for a period of time of sixty hours, such exposure failed to produce even the slightest evidence of oxide formation thereon. This characteristic is especially noted for the alloy containing from 5% to 7% of aluminum, it being found that, although the iron inclusions impart physical strength to the alloys containing smaller quantities of aluminum, the alloys containing smaller quantities of aluminum are not satisfactory as to their oxidation resistant characteristics.

From the. foregoing, it is quite apparent that a copper base alloy containing aluminum and iron within the range given is produced which can be cold worked similar to the binary alpha bronze alloys, while having the characteristics of being susceptible to precipitation hardening to impart high strength thereto. Further, since the alloy has the characteristic of retaining its high strength and of being resistant to oxidation when subjected to elevated temperatures, it will find many and varied applications where such characteristics are necessary.

Although this invention has been described with reference to a particular embodiment thereof, it is, of course, not to be limited thereto except insofar as is necessitated by the description thereof and the scope of the appended claims.

I claim as my invention:

l. An alloy comprising from'5% to 7% of aluminum, from 1% to 5% of iron, and the balance substantially all copper.

2. An alloy comprising about 5% of iron, about 7% of aluminum, and the balance substantially all copper.

3. An alloy comprising from 5% to 7% of aluminum, from 1% to 5% of iron, and the balance substantially all copper which has been quenched from a temperature of between 750 C. and 

